Demetalization Of Heavy Oil Based On Self-assembly Of Heavy Aromatics In Supercritical Water

The demetalization of heavy oil through pyrolysis in the presence of supercritical water(SCW)was experimentally investigated at the temperature of 653-663 K,water density of 0.10-0.30 g/cm~3 and water to oil ratio of 2:1-6:1(vol.),the reaction products were characterized and a five lump kinetics were established to study the process.At high water to oil ratio and high water density,the occurrence of pyrolysis can be transferred from the traditional oil phase into the SCW phase.Compared with the cracking in the oil phase,the cracking rate of heavy oil in SCW environment is significantly improved,and the acceleration effect is affected by the thermodynamic conditions of water.Driven by the ?-?attractive interaction between aromatic sheets and the superb diffusivity in SCW,the coke-like self-assembly of metal-containing heavy aromatics occurs spontaneously and rapidly.The self-assembly behavior of aromatics in SCW depends not only on the thermodynamic state of SCW but also on the average scale of aromatics.With the aid of self-assembly in dense SCW,the condensation of metal-containing heavy aromatics,distributed mainly in vacuum residue,to coke is significantly accelerated,by which the rate of demetalization is improved simultaneously.Owning to the preferential self-assembly of metal-rich heavy aromatics,an increasing yield of liquid products can also be obtained under optimized SCW environment.